I got the original iPhone, then upgraded to 3g, to 3gs, to blackberry bold, to nexus one, back to 3gs, then back to 3g. Then I finally got my iPhone 4. Hands down, the best smartphone I've used. Best is not always about what's under the hood, but how whatever is in it is utilized.
Battery kicks ass, screen looks amazing (the difference in readability between the 3g and the iPhoen 4 is huge!), it's fast (I expeirence almost no lag at all), design is amazing, Facetime is spectacular (never thought I'd even use facetime a lot, but my gf and I use it everyday since she still lives at home with her parents, used it last weekend when we were deciding which clubs to go to and I facetimed one of my friends who was at a club to see if it was crowded, AMAZING!), I actually get a constant >1.5mbs download on ATT 3g here in the DC metro area and couldn't be happier, I also carry around a sprint 4g3g overdrive hotspot which allows me to facetime on the go. I do drop calls once in awhile, but definitely less with the ip4 then when I had the 3g. The design is sexy. Build quality is great.
A lot of the poeple I know have been coming up to me and telling why I got it knowing the signal loss issue, I give them my phone and tell them to recreate the scenario, they try and always fail.
I too think iPhone 4 kicks major ass.